Study on the mechanical effects of cardiac assist by implantable sono-micrometer

1.设计了一种可植入微型传感器(直径2 mm)的8通道超声测微仪，用于测量室壁直径和心肌节段长度。急性动物实验在犬左心房与降主动脉之间或左心室与降主动脉之间放置左心室辅助装置(LVAD)，结扎左冠状动脉前降支以局部诱导缺血区。用超声传感器测量泵血和非泵血时的左心室内径和心肌节段长度，计算正常心肌和缺血心肌的左心室做功和局部做功。结果表明，LVAD可减轻正常心肌负荷，不会对缺血区造成过大负荷，在室主动脉间植入LVAD后，正常心肌做功降至接近于零。慢性动物实验采用与急性实验相同的方法，将心脏正常的山羊植入LVADs和超声传感器。研究发现，长期负重负荷会发展成心肌萎缩。对诱发心力衰竭山羊的实验结果表明，左心功能的恢复是由正常心肌的代偿功能所致。正常区可见心肌超微结构改变。

1. Ultrasonic displacement meter An eight-channel sono-micrometer with implantable miniature sensors (2 mm in diameter) was designed for the measurements of ventricular diameter and myocardial segment length.2. Acute animal experiments An left ventricular assist device (LVAD) was implanted between the left atria and the descending aortas or between the left ventricles and the descending aortas in dogs, whose left anterior descending coronary arteries were ligated to locally induce ischemic areas. The ultrasonic sensors were used to measure the left ventricular diameter and myocardial segment length during pumping and non-pumping, from which left ventricular work and local work done by the normal and ischemic myocardium were calculated. The results indicated that the LVAD unloads the normal myocardium and exerts no excessive load to the ischemic region, and that the normal myocardial work is reduced to near zero in the case of the implantation of LVAD between the ventricle and aorta.3. Chronic animal experiments Goats with normal hearts were implanted with the LVADs and the ultrasonic sensors by using the same way as used in the acute experiments. It was found that the long term unloading develops the myocardial atrophy. The results obtained from experiments on goats with induced heart failure showed that the recovery of the left ventricular function is brought about by the compensatory function done by the normal myocardium. The hypertorophy of the myocardium was observed in the normal area.